1. Field of the Invention
The invention generally relates to ceramic ferrule structures which are used for the protection of fire tubes and associated tube sheets used in sulfur plant boiler and cooler apparatus, the invention particularly relating to a double-ring ceramic ferrule having improved anchoring capability and increased resistance to tube erosion.
2. Description of the Prior Art
Devices capable of protectively insulating against heat flow through pipe structure have long been known in the art. In particular, concentric pipe structures particularly suited for low temperature insulation are disclosed by Kobres in U.S. Pat. No. 4,014,369. Fink, et al., and Bittner, in U.S. Pat. Nos. 3,409,731 and 3,626,987, respectively, disclose coaxial cable and coaxial piping systems wherein one member disposed concentrically of a second member is utilized to insulate portions of the total structure. Stocker, in U.S. Pat. No. 1,153,724, and Torti, in U.S. Pat. No. 3,318,340, disclose lining structures for pipes and the like, which protect the exterior portions of the assembly from corrosive materials or thermal effects of a material passing through the interior of the pipe. In the particular use situation to which the present invention provides improvement, that is, in the protection of fire tubes and associated tube sheets used in sulfur boilers and coolers, ceramic insert tubes have previously been used for disposition within a fire tube in order to prevent burn out of the fire tube by the high temperature gas flow normally directed through said fire tube. The ceramic tubular members presently used in such situations are subject to slippage from the fire tubes due to the fact that the single anchoring ring disposed on the exterior surface of the ceramic member at the inlet end of the fire tube is inadequate to maintain the ceramic member in place within the fire tube. Accordingly, such fire tubes and the associated tube sheets through which the fire tubes pass frequently burn out and are otherwise thermally damaged, thereby causing expensive replacement and maintenance problems. The present invention provides structure characterized by improved anchoring and protective capability, the present article of manufacture being particularly useful for protection of fire tubes and associated tube sheets in sulfur boilers utilized to extract sulfur from natural gas.